CNC - Center for Neuroscience and Cell Biology, Rua Larga, 1° Piso da FMUC, University of Coimbra, 3004-504, Coimbra, Portugal.
CFE - Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456, Coimbra, Portugal.
Sci Rep. 2018 Jan 11;8(1):464. doi: 10.1038/s41598-017-19087-y.
In carnivorous fish, conversion of a glucose load to hepatic glycogen is widely used to assess their metabolic flexibility towards carbohydrate utilization, but the activities of direct and indirect pathways in this setting are unclear. We assessed the conversion of an intraperitoneal glucose load (2 g.kg) enriched with [U-C]glucose to hepatic glycogen in juvenile seabass and seabream. C-NMR analysis of glycogen was used to determine the contribution of the load to glycogen synthesis via direct and indirect pathways at 48-hr post-injection. For seabass, [U-C]glucose was accompanied by deuterated water and H-NMR analysis of glycogen H-enrichment, allowing endogenous substrate contributions to be assessed as well. For fasted seabass and seabream, 47 ± 5% and 64 ± 10% of glycogen was synthesized from the load, respectively. Direct and indirect pathways contributed equally (25 ± 3% direct, 21 ± 1% indirect for seabass; 35 ± 7% direct, 29 ± 4% indirect for seabream). In fasted seabass, integration of H- and C-NMR analysis indicated that endogenous glycerol and anaplerotic substrates contributed an additional 7 ± 2% and 7 ± 1%, respectively. In fed seabass, glucose load contributions were residual and endogenous contributions were negligible. Concluding, direct and indirect pathways contributed equally and substantially to fasting hepatic glycogen repletion from a glucose load in juvenile seabream and seabass.
在肉食性鱼类中，将葡萄糖负荷转化为肝糖原广泛用于评估它们对碳水化合物利用的代谢灵活性，但在这种情况下直接和间接途径的活性尚不清楚。我们评估了腹腔内葡萄糖负荷（2 g.kg）在幼鲈和真鲷中的转化为肝糖原的情况。在注射后 48 小时，通过 C-NMR 分析肝糖原，确定负荷通过直接和间接途径合成糖原的贡献。对于鲈，[U-C]葡萄糖伴随着氘化水和 H-NMR 分析肝糖原 H-丰度，也允许评估内源性底物的贡献。对于禁食的鲈和真鲷，分别有 47 ± 5%和 64 ± 10%的糖原由负荷合成。直接和间接途径的贡献相等（鲈的直接途径为 25 ± 3%，间接途径为 21 ± 1%；真鲷的直接途径为 35 ± 7%，间接途径为 29 ± 4%）。在禁食的鲈中，H-NMR 和 C-NMR 分析的整合表明，内源性甘油和氨酰基供体分别贡献了另外的 7 ± 2%和 7 ± 1%。在禁食的鲈中，葡萄糖负荷的贡献是残余的，内源性贡献可以忽略不计。综上所述，直接和间接途径在幼鲈和真鲷从葡萄糖负荷中补充肝糖原方面贡献相等且显著。
